The production of a book or magazine involves a large number of processes. The processes may be grouped into five general categories: prepress, plate preparation, press set up or “make ready”; press control operations; and postpress operations.
In prepress, the principal processes are graphics, image and text editing and composition. In recent years, this area has undergone revolutionary changes through application of computer technology. State of the art systems for graphics and image editing and composition, as well as the specific functions of scanning, image processing and plotting include systems manufactured and sold by Scitex Corporation Ltd., Herzlia, Israel, such as, respectively, the systems sold under the trademarks Smart Scanner, Assembler and Raystar.
Plate preparation involves a technique known as imposition or signature assembly, which refers to the arrangement of pages on a film used to produce a printing plate. The present state of the art in signature assembly is the use of large and expensive machinery requiring highly skilled operators. Presently available signature assembly machinery involves the following steps: exposure of each of a plurality of separations (such as C, M, Y and K) for each of a plurality of pages to be arranged on a single plate; and subsequently, for each separation, such as C, feeding the exposed plurality of pages to an expose and repeat device such as the Misomex Master S Series, commercially available from Misomex North America Inc., Rosemont, Ill. The expose and repeat device is operative to arrange the plurality of exposed C separations, corresponding to the plurality of pages to be arranged on a single plate, at precisely determined positions on a film and to reproduce the C separations at the precisely determined positions by a photographic process.
The C printing plate is produced by contact exposure of the film. The signature is proofed prior to exposure of the plate. The plate, once exposed, is often found to be imperfect and therefore generally requires quality inspection and defect repair processes. The plate preparation process is repeated in order to produce M, Y and K plates.
Press set-up or “make-ready” takes place after preparation of the printing plate, and involves scanning of each printing plate to obtain information necessary for press set-up. This information includes the variation of the dot percentage over each plate, which determines the required ink flow for that plate.
Press control involves adjustments to the printing press which are normally made by a pressman examining the printed output from the press or by automatic press control systems such as the SPM 700, commercially available from Gretag Data and Image Systems, CH-Regensdorf, Switzerland. Automatic press control systems are operative to scan the printed output from the press compare it to a reference, such as a signature proof, and make suitable adjustments to the printing press. Post press processes include the folding, cutting and binding of the press output.
A great number of patents exist in the area of prepress. These include co-assigned U.S. Pat. No. 4,456,924 which describes method and apparatus for screen generation, co-assigned U.S. Pat. No. 4,853,709 which describes an internal drum laser plotter, and co-assigned U.S. application Ser. No. 044,428 which describes a color digital scanner.
Various processes in the production of printed matter are discussed in the following publications, the disclosures of which are incorporated herein by reference:
Alfred Furler, Folding in Practice, in collaboration with STAHL GMBH & Co., 3rd Edition, Germany, 1983;
William Schreiber, Fundamentals of Electronic Imaging Systems, Springer-Verlag, New York, 1986;
R. K. Molla, Electronic Color Separation, RK Publications, 1988; and
Michael H. Brill (Ed.), Perceiving, Measuring and Using Color, SPIE Proceedings, Vol. 1250, Billingham, Wash., USA, February 1990;
Robert A. Ulicheney, Digital Halftoning and Physical Reconstruction Function, Ph.D. Thesis, Massachusetts Institute of Technology, MA, USA, June 1986; and
Raymond Blair and Charles Shapiro (Eds.), The Lithographer's Manual, GATF, USA, 1980.
A state of the art printing press is described in U.S. Pat. No. 4,936,211 to Pensavacchia et al. Pensavacchia et al mention printing apparatus which is intended to achieve complete computer control over the entire printing process, including plate generation, ink regulation and the start-up, print, hold, shut-down and clean-up stages of the actual printing operation. Pensavacchia et al also refer to a press including a workstation which allows an operator to input a representation of an original picture to be printed. The workstation may include a CRT display and internal memory for storing image data so that the impression to be printed may be previewed before printing and a keyboard via which the operator may key in instructions regarding the particular press run such as the number of copies to be printed or the number of colors in the printed copies. The workstation also is intended to allow complete control over the operating modes of the press including printing plate imaging, press startup procedure, ink flow regulation, dampening, print, pause and shutdown and clean-up sequences.
Computer technology has also been proposed for use in facilitating certain stages of the imposition process as described in European Published Patent Application 0309196, published Mar. 29, 1989, European Published Patent Application 0348908, published Jan. 3, 1990 and in U.K. Patent 2128843, published on May 2, 1984. U.S. Pat. No. 4,150,991 describes one type of optical imposition machine mploying transparencies.